In 1999, Congress instructed the USPTO to extend the term of each issued patent to account for any delays during prosecution caused by the USPTO (offset by delays caused by the applicant).  

In Wyeth and Elan Pharma International, Ltd. v. Under Sec. of Commerce for Intellectual Property (2009-1120, 7 January 2010, precedential), the USPTO's reviewing court, the Court of Appeals for the Federal Circuit found that the USPTO had been taking a "strained interpretation" of that law, that is, the USPTO's approach "cannot be reconciled with the language of the statute", and was effectively swiping a portion of the term extensions to which certain patent applications were entitled.  Hopefully, the Court's decision will keep the USPTO out of this particular cookie jar.